Stroke transmission gear mechanism, and electric toothbrush having such a gear mechanism

ABSTRACT

Electric toothbrushes have a replaceable head part having a brush head and a hand part provided with a drive motor for the brush. When a head part is pushed onto the hand part, a drive pin which performs an axial stroke motion is connected to the brush head. A gear mechanism in the head part transmits the stroke motion of the drive pin, for example in a stroke motion of the brush head, upon which a lateral tilting motion is superimposed. However, the stroke of the drive pin provided by some hand parts is not matched to the desired stroke of the brush head. Therefore, a stroke transmission gear mechanism is provided in the head part in the mechanical linkage between the drive pin and the brush head, the drive rod of the stroke transmission gear mechanism being connected to the drive pin, and the stroke transmission gear mechanism in particular is installed in such a way that a stroke reduction occurs. In this manner it is possible for the stroke supplied by the drive pin to be translated into a stroke that is matched to the brush head.

The invention relates to a stroke transmission gear mechanism, in particular for an electric toothbrush, to translate an oscillating stroke motion of a drive rod into an oscillating amplitude-modified stroke motion of an output rod, with a transmission lever which is pivotable about a swivel bearing being provided between the two rods, both of which are linked to the transmission lever at different distances from the swivel bearing.

In such gear mechanisms, the problem lies in implementing the gear mechanism with as few articulating joints as possible to minimize susceptibility to malfunction. The gear mechanisms should also be extremely easy to manufacture to ensure suitability for mass production.

This problem is solved according to the invention by connecting the drive rod to the end of the transmission lever opposite from the swivel bearing via a hinge, and by holding the other end of the transmission lever in the swivel bearing in a displaceable manner.

Such a solution enables at least one of the rods to be directly connected to the transmission lever in an articulated manner, since the displaceable arrangement of the transmission lever allows it to yield when, in addition to the pivoting motion, a longitudinal motion is imposed on it by the stroke of the drive rod.

In particular, the drive rod may have a laterally stepped projection on its front end to which the transmission lever is pivotably mounted in a hinge. This also allows a configuration in the smallest possible space, since the transmission lever may be aligned approximately perpendicular to the drive rod and during its pivoting motion is therefore able to swing over the projection.

The displaceable bearing of the transmission lever may be implemented relatively easily by providing the other end of the transmission lever with a slot through which a pin projects which is stationarily mounted to the gear mechanism and which forms the pivot axis of the transmission lever. In this configuration the end of the transmission lever is thus designed as a fork which encloses the pin, so that during its pivoting motion the transmission lever can simultaneously undergo a longitudinal motion.

The output rod together with the drive rod is located in a stationary guide which allows only longitudinal motion but no transverse motion. For this reason a transmission rod connected to the output rod must be linked to the transmission lever via a hinge, and the transmission rod performs a pivoting motion corresponding to the up and down motions of the transmission lever.

In order to place the output rod in an oscillating rotational motion about its longitudinal axis, the invention provides that the transmission rod is connected to the output rod via a ball joint, and the output rod is guided into a slot running obliquely to the longitudinal axis of the output rod.

Provided that the load on the gear mechanism is not too great, as is the case for an electric toothbrush, for example, at least the transmission lever, the projection, and the transmission rod may be fabricated from plastic, and the hinges may be designed as film hinges.

The invention further relates to an electric toothbrush having a hand part provided with a drive, a drive pin which performs at least one axial stroke motion projecting at the slip-on end of the hand part, and a head part, which can be pushed onto the slip-on end of the hand part, in which a brush head which bears bristle tufts is mounted so that it can perform at least one back-and-forth stroke motion in the longitudinal direction of the head part, for which purpose the brush head is connected to the drive pin when the head part is pushed onto the hand part.

It is problematic that conventional drives which are intended to produce a rotational motion of the brush head about its vertical axis, for example, require a relatively large stroke of the drive pin. Therefore, such a hand part could not be readily combined with a head part, the brush head of which is intended to perform only a small stroke motion. Although it is conceivable that a separate hand part could be provided for such a head part, it is disadvantageous that the user would need several hand parts if the user wanted to use different brush heads for brushing the teeth.

This problem is solved according to the invention by providing a stroke transmission gear mechanism in the head part in the mechanical linkage between the drive pin and the brush head, the drive rod of the stroke transmission gear mechanism being connected to the drive pin, and by installing the stroke transmission gear mechanism in particular in such a way that a stroke reduction occurs.

This solution also has the advantage that the head part having a brush head which moves back and forth can be matched to existing hand parts having a specified stroke of the drive pins by merely adjusting the multiplication or reduction ratio of the stroke transmission gear mechanism, which is possible with minimal design engineering measures.

In principle, the stroke transmission gear mechanism may also be provided in an adapter which is first attached to the hand part.

Such toothbrushes are frequently provided with a replaceable head part to enable the toothbrush head to be exchanged from time to time for hygienic reasons. The invention therefore provides that the toothbrush comprises a hand part and a head part, an electric drive for the drive rod being furnished in the hand part, and that the gear mechanism in the head part is housed and mounted in the head part. Consequently, the gear mechanism described above is an integral component of the head part and is substituted by same. For this reason, everything must have a relatively simple design and be economical to manufacture. On the other hand, the requirements for durability of the gear mechanism are not very great, since it is assumed that the head part must be replaced after approximately 500 to 1000 tooth brushing operations.

The invention is explained in greater detail below with reference to one exemplary embodiment. The figures show the following:

FIG. 1 shows a side view of the gear mechanism according to the invention;

FIG. 2 shows an exploded illustration of the head part of an electric toothbrush;

FIG. 3 shows a longitudinal section through this head part; and

FIG. 4 shows an exploded illustration of the gear mechanism in a cylinder composed of two half-shells.

Reference is first made to FIG. 1, which shows the gear mechanism 1 according to the invention. A drive rod 2 and an output rod 3 are situated in the coaxial direction inside a housing 19, which in this exemplary embodiment is formed by the head part of an electric toothbrush. Between the two mutually facing ends of the rods 2, 3 a cylindrical transmission lever 4 is located in the vertical position, which on one end has the shape of a fork 5 which is pushed onto a pin 6.

The other end of the transmission lever 4 is beveled, and merges into an edge 8 which is connected via a film hinge 9 to a projection 10 which laterally protrudes from the drive rod.

Below the fork 5 a bar 11 is located which projects laterally from the transmission lever 4 and which is connected to a short transmission rod 13 via an additional film hinge 12. The other end of the transmission rod 13 has a ball head 14 which is inserted or snapped into a ball socket 15 at the end of the output rod 3.

Two sliding blocks 16, which are guided into slots (not illustrated here) in the housing 19, are located on the side of the output rod 3 and simultaneously impart an oscillating rotational motion to the output rod 3 on account of their longitudinal motion.

The gear mechanism operates as follows: The drive rod 2 is placed in a back-and-forth motion by a drive, not illustrated here. This motion is transmitted via the film hinge 9 to the transmission lever 4, which imparts a pivoting motion about the pin 6. The pivoting motion is transmitted to the transmission rod 13 and thus to the output rod 3, the stroke of the latter being shorter than that of the drive rod 2 since the transmission rod 13 engages with the transmission level with a shorter stroke path length than does the drive rod 2.

FIG. 2 shows an exploded illustration of the head part 20 of an electric toothbrush. This head part comprises the previously mentioned housing 19 in which the above-described gear mechanism 1 is situated. The output rod 3 has a projection in the form of a plate 21, situated below an opening 22 in the housing 19, on the top side of which a brush bristle holder 23 is attached. The underside of the housing 19 is closed off by a shell-like cover 24. As seen in FIG. 3, guides 25 for the rods 2, 3 and for the plate 21 are located in the housing 19.

The gear mechanism 1 is housed in a two-part cylinder 30 which can be inserted into the head part 20. This cylinder is composed of two interlocked half-shells 31 a, 31 b.

The cylinder 30 forms a guide for both the drive rod 2 and the output rod 3. In addition, a slot 33 for the sliding block 16 provided as a transverse rod 34 is embedded at one end.

The cylinder 30 has two oppositely-situated openings 35, 36 for the transmission lever 4 which are formed by open-edge recesses in the edges of the half-shells 31 a, 31 b.

At one opening, enlarged areas 37, 38 having oppositely-situated flush blind holes are located in which the pin 6 for the transmission lever 4 is inserted.

On the exterior of the cylinder 30 are located additional longitudinal bars 39 which are introduced into corresponding grooves in the head part 20, thereby preventing the cylinder 30 from rotating at that point.

List of Reference Numbers

-   1 Gear mechanism -   2 Drive rod -   3 Output rod -   4 Transmission lever -   5 Fork -   6 Pin -   8 Edge -   9 Film hinge -   10 Projection -   11 Bar -   12 Film hinge -   13 Transmission rod -   14 Ball head -   15 Ball socket -   16 Sliding block -   19 Housing -   20 Head part -   21 Plate -   22 Opening -   23 Brush bristle holder -   24 Cover -   25 Guide -   30 Cylinder -   31 a Half-shell -   31 b half-shell -   33 Slot -   34 Transverse rod -   35 Opening -   36 Opening -   37 enlarged area -   38 Enlarged area -   39 Longitudinal bars 

1. A stroke transmission gear mechanism for an electric toothbrush to translate an oscillating stroke motion of a drive rod into an oscillating amplitude-modified stroke motion of an output rod, comprising a transmission lever which is pivotable about a swivel bearing being provided between the two rods, both of which are linked to the transmission lever at different distances from the swivel bearing, wherein the drive rod is connected to the end of the transmission lever opposite from the swivel bearing via a hinge, and the other end of the transmission lever is held in the swivel bearing in a displaceable manner.
 2. A gear mechanism according to claim 1, wherein the drive rod has a laterally stepped projection on its front end to which the transmission lever is pivotably mounted in a hinge.
 3. A gear mechanism according to claim 2, wherein the other end of the transmission lever has a slot through which a pin projects which is stationarily mounted to the gear mechanism and which forms the pivot axis of the transmission lever.
 4. A gear mechanism according to claim 3, wherein a transmission rod connected to the output rod is linked to the transmission lever via a hinge.
 5. UA gear mechanism according to claim 4, wherein the transmission rod is connected to the output rod via a ball joint, and the output rod is guided into a slot running obliquely to the longitudinal axis of the output rod.
 6. A gear mechanism according to claim 4, wherein at least the transmission lever, the projection, and the transmission rod are fabricated from a plastic, and the hinges are film hinges.
 7. An electric toothbrush comprising a hand part provided with a drive, a drive pin which performs at least one axial stroke motion projecting at the slip-on end of the hand part, and a head part, which can be pushed onto the slip-on end of the hand part, in which a brush head which bears bristle tufts is mounted so that it can perform at least one back-and-forth stroke motion in the longitudinal direction of the head part, for which purpose the brush head is connected to the drive pin when the head part is pushed onto the hand part, a stroke transmission gear mechanism is provided in the head part in the mechanical linkage between the drive pin and the brush head, the drive rod of the stroke transmission gear mechanism being connected to the drive pin, and the stroke transmission gear mechanism in particular is installed in such a way that a stroke reduction occurs.
 8. A toothbrush comprising a hand part provided with a drive, a drive pin which performs at least one axial stroke motion protecting at the slip-on end of the hand part, and a head part, which can be pushed onto the slip-on end of the hand part, in which a brush head which bears bristle tufts is mounted so that it can perform at least one back-and-forth stroke motion in the longitudinal direction of the head part, for which purpose the brush head is connected to the drive pin when the head part is pushed onto the hand part, a stroke transmission gear mechanism provided in the head part in the mechanical linkage between the drive pin and the brush head, the drive rod of the stroke transmission gear mechanism being connected to the drive pin, and the stroke transmission gear mechanism in particular is installed in such a way that a stroke reduction occurs, wherein the stroke transmission gear mechanism is as claimed in claim
 1. 9. A toothbrush according to claim 8, wherein the output rod is provided with a head which bears one or more bristle tufts.
 10. A toothbrush according to claim 9, wherein the ball joint is formed from a ball head on the transmission rod and a ball socket on the output rod. 